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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Stanovení kinetiky polymerace propenu na Zieglerových-Nattových katalyzátorech metodami násadové polymerace a Stopped-Flow za průmyslových podmínek / Determination of propene polymerization kinetics on Ziegler-Natta catalysts by methods of batch and Stopped-Flow polymerization performed under industrial conditions

Tvrdý, Michal January 2019 (has links)
This thesis is focused on the determination of the propene polymerization kinetics on phthalate and nonphthalate diester Ziegler-Natta MgCl2-supported catalysts under the industrial conditions. The kinetic profiles were determined by various laboratory techniques for propene polymerization. For assessing the profiles were utilized batch gas and liquid polymerization modes in 2-litre and 4-litre reactors. Finally, the results were complemented with the runs performed in a unique Stopped-Flow apparatus, which allows polymerization of liquid propene at very short polymerization times. The kinetics profiles of both catalysts were determined and compared by combination of experimental data of these techniques. The basic properties of the synthesized polymeric powders were measured, such as the melt flow index, bulk density and amount of polypropene fraction soluble in cold xylene.
72

Vliv katalytického systému na strukturu E/P kopolymerů / Effect of catalystic system on the structure of E/P copolymers

Kolomazník, Vít January 2019 (has links)
Thesis is focused on structural study of ethylene-propylene copolymers (E/P copolymers) produced by gas phase polymerization. Goal of work was to determine the effect of used catalysts on the distribution of ethylene units in the resulting material. Three E/P copolymers were prepared on commercial Ziegler Natta catalysts with diether or phthalate based internal donors. The copolymers were fractionated according crystallization ability and molar mass. Next, the mass content and the distribution of the ethylene units in the copolymer were determined in each fraction by nuclear magnetic resonance (NMR). Together with other structural analytical methods, phthalate internal donor has been found to produce ethylene blocks under certain conditions, while the diether ID lacks this ability.
73

Vliv přídavku ethenu na aktivitu Z-N katalyzátoru pro nízkotlakou polymeraci propenu / Influence of Ethene Addition on Ziegler-Natta Catalyst Performance in Low-pressure Propene Polymerization

Hoza, Adam January 2010 (has links)
The aim of the study will be the determination of the kinetic profiles of the polymerization of propene, ethene and their mixtures with commercial Ziegler-Natta catalyst by application of two different experimental procedures. The prepared polymer material will be utilized for the SEC analysis and subsequent evaluation of the concentration of active sites. The determined molecular mass distribution curves will be further investigated by the application of the procedure, which deconvolute the overall profile on the basic Flory's distribution functions. Then the comprehensive study about character and behavior of various types of active centers in dependence on time and type of monomer will result from this investigation.
74

Study of ethylene/propylene polymerization, using a 4th generation Ziegler-Natta catalyst: Effect of external donor and feed ratio on polymerization

Shafagh Dehghani, Seyedeh January 2012 (has links)
A fourth generation multiple site Ziegler-Natta catalyst was used to synthesize ethylene and propylene homo-and copolymers in the presence of hydrogen. This type of catalysts produce polymers with broader molecular weight distribution (MWD), chemical composition distribution (CCD) and stereoregularity than other coordination polymerization catalysts since it has more than one active site. The ratio of propylene/ethylene was varied to study its effect on polymer microstructure. In addition, by having two different electron donors, namely diisopropyldimethoxysilane (P) and dicyclopentyldimethoxysilane (D), the molecular weight distribution (MWD) and stereospecificity of the synthesized polymers were examined. The polymer samples were characterized using 13C-NMR and high-temperature gel permeation chromatography (GPC). Using the 13C-NMR data, the triad distribution for the copolymers and also the isotactic triad distribution for homo-polymers were calculated. The effects of electron donors on different feed ratios of ethylene and propylene in the synthesis were investigated. Co-polymer produced with D-donors showed higher isospecificity and also higher content of ethylene in the final polymer. In contrast, polymers produced using with P-donor showed lower polydispersity indices (PDI), and had higher contents of propylene in final polymer. In addition, the “Deconvolution method” was applied to GPC data in order to determine the number of sites on the Ziegler-Natta catalyst; which showed that 4 active site types were adequate to explain the molecular weight distributions.
75

Automatic tuning of Electro-Optical Director

Berner, Marcus January 2009 (has links)
Directors designed for observation and fire control in naval environments consist of a mechanical pedestal moved by two electrical motors. To meet the high demands on director precision, a servo solution based on feedback control is used. The digital servo controller has to be tuned to meet demands on performance and stability. This report presents methods for automatic tuning, intended to replace today’s manual tuning procedures. System identification based on relay feedback and recursive least-squares approximations are combined with the Ziegler-Nichols and AMIGO tuning procedures for PI controllers are evaluated. Evaluations are performed in simulations, for which a SIMULINK model is constructed. Results indicate that the automatic tuning may perform well compared to the manual tuning used today, and that it could bring considerable reduction in the time required for tuning.
76

Synthese, Struktur und Reaktivität von [2]Borametallocenophanen der Gruppe 4 Metalle : Ihr katalytisches Verhalten und die Eigenschaften der erhaltenen Polymere / Synthesis, structure and reactivity of [2]borametallocenophanes of group 4 metals : Their catalytic behaviour and properties of the obtained polymers

Öchsner, Andreas January 2009 (has links) (PDF)
In der vorliegenden Arbeit wird die Darstellung einer Reihe monoarylsubstituierter Bisdimethylamino-1-bromo-2-arlydiborane(4) beschrieben. Sowohl die Umsetzung der monoarylsubstituierten Ligandenvorstufen mit einem weiteren Äquivalent Lithium- oder Natriumaryl in einem Ether/Toluol-Gemisch als auch die Umsetzung von 1,2-Dibrom-bis(dimethylamino)diboran(4) mit einem mehrfachen Überschuss Lithium- oder Natriumaryl führte zur Bildung von diarylsubstituierten Diboranen(4). Umsetzung der Ligandenvorstufen mit Lithiumorganylen, wie beispielsweise Li[CH3] oder Li[C4H9] führt zu doppelt deprotonierten Verbindungen. Werden die dilithiierten Verbindungen mit Metallhalogeniden der Gruppe 4 in einem Toluol/Ether-Gemisch umgesetzt, können [2]Borametallocenophane erhalten werden. Von einigen der Verbindungen konnte die Struktur im Festkörper mittels Einkristallstrukturanalyse bestimmt werden. Die Verbindungen zeigen in Lösung ein dynamisches Gleichgewicht, welches durch die Flexibilität der B-B-Brücke ermöglicht wird. Dieses konnte mittels NMR Spektroskopie untersucht werden. Auch die Reaktivität der Verbindungen wurde erforscht. Versuche zur oxidativen Addition von Platin(0) in die B-B-Bindung, wie sie bereits für ähnliche Systeme beschrieben waren, scheiterten. Ebenfalls nicht erfolgreich war der versuchte Austausch der Dimethylaminogruppen an den Bor-Atomen. Di(fluorenyl)substituierte [2]Borametallocenophane zeigen in der Reihe der dargestellten Verbindungen ein einzigartiges Verhalten. Wird die dilithiierte Liganden-Vorstufe bei der Umsetzung mit den Metallhalogeniden der Gruppe 4 Licht ausgesetzt, so lagert sie zum 1,3-Diboretan um. Auch oxidativ kann diese Umlagerung ausgelöst werden. Das Umlagerungsprodukt war von anderen Reaktionen bereits bekannt, konnte im Rahmen dieser Arbeit aber erstmals strukturell charakterisiert werden. Die Dichloroverbindungen der [2]Borametallocenophane können mittels Li[CH3] in die entsprechenden Dimethylkomplexe überführt werden. Damit besteht die Möglichkeit, die Verbindungen nicht nur mit MAO, sondern auch mit alternativen Co-Katalysatoren, wie beispielsweise Tris-(pentafluorphenyl)boran für die Olefinpolymerisation zu aktivieren. Die Aktivierung mittels MAO wurde sowohl mittels NMR- als auch mittels UV/Vis-Spektroskopie bei verschiedenen [Al]/[Zr] Verhältnissen untersucht. Neben den [2]Borametallocenonphanen konnte mit Verbindung [(n5-C29H37)2ZrCl2] das erste Metallocen mit dem neuen OctafluH-Liganden und zwei koordinierenden Arylgruppen dargestellt werden. Um die Polymerisationseigenschaften der Verbindungen zu untersuchen, wurde ein neuer Versuchsaufbau entworfen. Zur Überwachung der Polymerisationen wurde ein Programm entwickelt, was in der Lage war, verbrauchte Gasmenge und Temperatur im Reaktoraufzuzeichnen. Hier wurden die katalytischen Eigenschaften einer Serie von [2]Borametallocenophanen und des dargestellten Metallocens [(n5-C29H37)2ZrCl2] in der Ethen-Homopolymerisation untersucht. Diese Polymere wurden mittels DSC auf ihre thermischen Eigenschaften hin geprüft. Ausgewählte Polymere wurden in Zusammenarbeit mit der LyondellBasell Industries, Basell Polyolefine GmbH, Frankfurt mittels GPC auf ihr mittleres Molekulargewicht und dessen Verteilung hin untersucht. Alle Daten wurden mit denen von industriell verwendeten Katalysatoren und den von Kraft bekannten [1]Borametallocenophanen verglichen. In weiteren Untersuchungen wurde überprüft, in wie weit die Polymerisationsbedingungen, wie beispielsweise das [Al]/[Zr]-Verhältnis, die Temperatur oder der Druck Auswirkungen auf die Eigenschaften des Polymers haben. Eine Reihe von Komplexen wurde überdies in der Ethen/[1]Hexen-Copolymerisation untersucht. Die erhaltenen Copolymere wurden mittels DSC-, GPC-, IR- und NMR- Spektroskopie analysiert. Zusammenfassend lässt sich feststellen, dass eine Reihe neuer Verbindungen dargestellt und charakterisiert werden konnte, wobei insbesondere der neuartige Ligand OctafluH (C29H38) eingesetzt wurde. Die dargestellten [2]Borametallocenophane sind aktive Katalysatoren in der Ziegler-Natta ähnlichen Olefinpolymerisation. Die dargestellten Polymere wurden mittels verschiedener Methoden untersucht. Es zeigte sich, dass [2]Borametallocenophane langkettige Polyolefine und Ethen/1-Hexen Copolymere liefern können. / Based on Krafts work on [1]borametallocenophanes, a various number of monoarylsubstituted bisdimethylamino-1-bromo-2-aryldiboranes(4) were synthesized in the present work. Either the reaction of these monoarylsubstituted compounds with one equivalent of a lithiumaryl in toluene/ether or direct reaction of 1,2-dibromo-bis(dimethylamino)diborane(4) with a large excess of the lithiumaryl leads to the formation of diaryl substituted diboranes(4). Reaction of the ligand precursors with lithium organyls, e.g. Li[CH3] or Li[C4H9] leads to double deprotonation. [2]Borametallocenophanes are accessible via reaction of the dilithiated species with metal halides of Group 4 in toluene/ether. Due to the flexibility of the B-B-bridge, these complexes show dynamic behaviour in solution, which can be monitored by NMR spectroscopy. The solid state structure of some of these complexes could be examined by X-Ray diffraction. The reactivity of the new [2]borametallocenophanes also was reviewed. An oxidative addition reaction of platinum(0) was published for similar systems, but failed in this case. Neither was it possible to substitute the bisdimethylamino-groups bound to the boron-atoms. The prepared di(fluorenyl)substituted [2]borametallocenophanes show a unique feature. If the dilithiated precursor is exposed to visible or UV light during reaction with metal halides of group 4, these complexes rearrange to the 1,3-diboretane. This rearrangement also can be performed oxidatively. The Compound has been previously characterized in solution by multinuclear NMR spectroscopy; its structure in the solid state is now reported for the first time. The [2]borametallocenophanedichlorides can be reacted with Li[CH3], resulting in the corresponding dimethyl complexes. This allows for an alternative activation of the complexes with co-catalysts like tris(pentafluorophenyl)borane, in addition to the common activation with MAO. A model reaction for this alternative activation was performed using K[B(C6F5)4] to obtain a ion pair via chlorine abstraction. The common activation of the metal complexes using MAO was monitored either by NMR- or by UV/Vis-spectroscopy at various [Al]/[Zr] ratios. In addition to the [2]borametallocenophanes, [(n5-C29H37)2ZrCl2] could be prepared. It is the first metallocene with two aryl groups of the new octafluH-ligand (C29H38). To analyse the activity of the compounds in olefin polymerization processes, a new experimental set-up was designed. To control the polymerisation reactions, a Software program was developed, which allowed us to record gas-consumption and temperature in the reactor simultaneously. The catalytic behaviour of a whole series of [2]borametallocenophanes and of compound [(η5-C29H37)2ZrCl2] was studied in ethene homopolymerization. The thermal properties of all produced polymers where analyzed by DSC. The molecular weight distribution of selected examples was studied in cooperation with LyondellBasell Industries, Basell Polyolefine GmbH with GPC analyses. All data where directly compared to reference catalysts and to the [1]borametallocenophanes made by Kraft. The data show, that [2]borametallocenophanes have lower activities than [1]borametallocenophanes, but produce polymers of significantly higher average molecular weight. One can see clear differences throughout the data of the DSC measurements, for instance in the melting point and metling range, or crystallinity of the polymer. The melting points of the polymers obtained from [2]borametallocenophanes and compound [(n5-C29H37)2ZrCl2] are significantly higher than those of the reference catalysts. Additional experiments gave some insight into the relationship between polymerization conditions, e.g. the [Al]/[Zr] ratio, temperature or pressure and the key features of the polymers. It was shown that all these parameters influence the melting point and other specific values of the polymer. Additionally, selected examples were tested in the ethene/1-hexene copolymerization. The copolymers have been analyzed using DSC, GPC, IR and NMR spectroscopy. In conclusion, some new products were prepared and analyzed, in many cases with OctafluH (C29H38) as a substituent. All [2]borametallocenophanes are active catalysts in Ziegler-Natta type olefin polymerization processes. Analyses of the produced polymers revealed that [2]borametallocenophanes can produce long-chain polyethylene and ethene/1-hexene copolymers.
77

Predictive Modeling of Metal-Catalyzed Polyolefin Processes

Khare, Neeraj Prasad 08 December 2003 (has links)
This dissertation describes the essential modeling components and techniques for building comprehensive polymer process models for metal-catalyzed polyolefin processes. The significance of this work is that it presents a comprehensive approach to polymer process modeling applied to large-scale commercial processes. Most researchers focus only on polymerization mechanisms and reaction kinetics, and neglect physical properties and phase equilibrium. Both physical properties and phase equilibrium play key roles in the accuracy and robustness of a model. This work presents the fundamental principles and practical guidelines used to develop and validate both steady-state and dynamic simulation models for two large-scale commercial processes involving the Ziegler-Natta polymerization to produce high-density polyethylene (HDPE) and polypropylene (PP). It also provides a model for the solution polymerization of ethylene using a metallocene catalyst. Existing modeling efforts do not include physical properties or phase equilibrium in their calculations. These omissions undermine the accuracy and predictive power of the models. The forward chapters of the dissertation discuss the fundamental concepts we consider in polymer process modeling. These include physical and thermodynamic properties, phase equilibrium, and polymerization kinetics. The later chapters provide the modeling applications described above. / Ph. D.
78

Análise de controle de força usando servomecanismo eletropneumático / Analysis of force control using electropneumatic servomechanism

Araujo, Eudes Gonzaga de 31 March 2015 (has links)
Submitted by Maria Suzana Diniz (msuzanad@hotmail.com) on 2015-11-12T13:26:59Z No. of bitstreams: 1 arquivototal.pdf: 1771439 bytes, checksum: 5a0ce436783e1a04419dc8a73bf4c204 (MD5) / Made available in DSpace on 2015-11-12T13:26:59Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1771439 bytes, checksum: 5a0ce436783e1a04419dc8a73bf4c204 (MD5) Previous issue date: 2015-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work presents the designs and results obtained through simulation and experimental testing of conventional controllers P, PI and PID implemented by personal computers applied to an electropneumatic servomechanism for control of force. The system consists of a double acting pneumatic cylinder, which is responsible for applying the force on a mechanical subsystem consisting of a spiral spring, representing the means of working. The proportional electropneumatic flow valve, being the element controlling the flow of compressed air to be released into the pneumatic air cylinder which results in controlled force application; a load cell converts the force applied by the cylinder onto the medium into an electrical signal. The control signal to be applied on the electropneumatic proportional flow valve comes from a signal input and output plate installed on the computer, which is controlled by an algorithm implemented in the computing environment LabVIEW®, wherein the mentioned controllers are inserted, the mathematical representative model of the servomechanism was obtained by applying the parametric identification technique Box-Jenkins (BJ) which results in a family of four models, one of which is chosen to represent the system. The adjustment of the controllers is done by using the critical gain method of Ziegler and Nichols so that the response from the system meets the performance specifications imposed on it. Simulated and experimental results of the system are presented under the inserted controllers, which are analyzed according to relevant theory to the study of conventional controllers; it appears then that the PID controller is best suited for use in its electropneumatic servomechanism. / Neste trabalho apresenta-se os projetos e resultados obtidos através de simulações e ensaios experimentais de controladores convencionais P, PI e PID implementado por computador pessoal aplicado em um servomecanismo eletropneumático para controle de força. O sistema é constituído por um cilindro pneumático de dupla ação, sendo este responsável pela aplicação da força sobre um subsistema mecânico constituído por uma mola helicoidal, representando o meio de trabalho. A válvula eletropneumática proporcional de vazão, sendo o elemento de controle da vazão de ar comprimido a ser liberada para o cilindro pneumático que resulta na aplicação da força controlada; uma célula de carga converte a força aplicada pelo cilindro sobre o meio em sinal elétrico. O sinal de controle a ser aplicado na válvula eletropneumática proporcional de vazão é proveniente de uma placa de entrada e saída de sinais instalada no computador, sendo esta comandada por um algoritmo implementado no ambiente computacional LabVIEW®, no qual os referidos controladores estão inseridos. O modelo matemático representativo do servomecanismo foi obtido aplicando-se a técnica de identificação paramétrica Box-Jenkins (BJ) da qual resulta uma família de quatro modelos, dos quais um é escolhido para representar o sistema. O ajuste dos controladores é feito utilizando-se a técnica do ganho crítico de Ziegler e Nichols, de modo que a resposta do sistema atenda as especificações de desempenho impostas ao mesmo. Resultados simulados e experimentais do sistema são apresentados sob ação dos controladores inseridos, que são analisados de acordo com a teoria pertinente ao estudo dos controladores convencionais; verifica-se então que o controlador PID é o mais adequado para utilização no respectivo servomecanismo.
79

Reglering av drönare vid viktbelastning / Control of drone with applied weights

Johansson, Simon January 2018 (has links)
I detta arbeta gjordes en undersökning om hur en drönare kan regleras vid olika viktbelastningar. Först gjordes en teoretisk undersökning av fyra olika reglermetoder, två modellbaserade och två icke-modellbaserade metoder. De två modellbaserade var linjär kvadratisk reglering och modell prediktiv kontroll. De två icke-modellbaserade var kaskad kontroll och PID regulator. Av alla metoderna valdes det att användas en PID regulator för regleringen. För att ställa in PID testades tre olika metoder, Ziegler-Nichols, lambda och AMIGO metoden. Alla dessa tre använde stegsvaret för systemet för att beräkna parametrarna till PID. Detta resulterade i flera olika parameterval för systemet. Parametervalen testades på drönaren och AMIGO metoden gav de bästa resultaten. De olika lasterna som testades var 4.7, 6.1 och 10.8 gram. AMIGO metoden kunde användas för att reglera drönaren upp till 6.1 gram därefter blev drönarens beteende allt för olinjärt. Sammanfattningsvis går det att använda en PID som ställs in med AMIGO metoden från stegsvaret för att reglera en drönare med mindre laster upp till ungefär sex gram. / This project tested how a drone can be controlled when loads are applied to it. First four different control methods were analyzed, two model based and two non-model based. The two model based were linear quadratic regulator and model predictive control. The two non-model based were cascade control and PID regulator. The PID regulator were chosen and three different methods to tune the PID was tested. Ziegler-Nichols, lambda and AMIGO method, all used the step response from the system to determine the parameters. These different methods gave different setup of parameters and the best result came from the AMIGO method. The different loads that were applied to the system was 4.7, 6.1 and 10.8 gram. The AMIGO method were able to tune the PID up to 6.1 grams, then the system lost to much of its linear behavior. To summarize the work a PID tuned by the AMIGO method using the step response were able to control a drone with a load up to about six grams.
80

Estrategias de regulación de frecuencia en unidades generadoras hidráulicas

Villanueva Mayr, Tomás Ignacio January 2016 (has links)
Ingeniero Civil Eléctrico / Una de las principales variables a controlar en un sistema eléctrico es la frecuencia. Para asegurar su estabilidad en las 2 etapas de control (control primario (CPF) y secundario de frecuencia (CSF)) se hace imprescindible un correcto ajuste de las ganancias de los reguladores involucrados. A través de esta memoria se busca proponer una metodología para el ajuste óptimo de reguladores PI encargados del CPF, los cuales pueden ser de frecuencia o potencia-frecuencia. Existe una infinidad de técnicas para definir los parámetros de los reguladores PI, no obstante no todas se ajustan al contexto de regulación de frecuencia utilizando centrales hidráulicas. En esta memoria se estudiaron 2 metodologías: ajuste según Bode y según Ziegler-Nichols. A través de un modelo lineal se aplicaron dichas metodologías al caso particular de la central Colbún. Luego, llevando los mismos ajustes a un modelo no lineal del sistema, se evaluó el desempeño de los reguladores para distintos escenarios y configuraciones: operación en isla y red; distintos niveles de potencia; diferentes niveles de cota de embalse. Para los casos en que la central opera con una cota alta y ésta se encuentra en la sección ancha de la chimenea de equilibrio que posee el sistema, los resultados muestran una respuesta que cumple con las exigencias presentadas en la Norma Técnica. Sin embargo, para cotas inferiores, cuando la cota pasa a la sección angosta de la chimenea, se observan respuestas no acorde a lo exigido. Para ello fue necesario proponer ajustes adicionales. De los resultados se observó que con el reajuste propuesto se cumplen con las exigencias de la Norma Técnica. Luego de establecer una comparación entre las respuestas del modelo no lineal y lineal, se obtuvo que para las condiciones de cota alta es posible utilizar el modelo lineal como una buena aproximación del no lineal. Luego, el análisis realizado para el CSF se realizó utilizando el modelo lineal. Se empleó un modelo de 2 centrales, con 2 generadores en cada una, donde una central se encarga exclusivamente del CPF mientras que la otra se encarga del CSF. Se ajustaron los principales parámetros del regulador encargado del CSF: la constante de tiempo del bloque integral y la tasa de toma de carga de las unidades. A través de las simulaciones se observó que el ajuste cumple con las exigencias fijadas por la Norma Técnica. El Artículo 3-17 de la Norma Técnica propone 2 alternativas para el control secundario de frecuencia: un control centralizado en el CDEC y uno localizado en una central (en este caso Colbún). Utilizando el sistema mencionado en el párrafo anterior, se estudiaron y compararon ambas alternativas. Se observó que la opción de un control localizado en una central es una solución simple, eficiente y viable, mientras que la alternativa de un control centralizado conlleva dificultades como lo son la presencia de oscilaciones sostenidas en el tiempo (ciclos límite), las cuales se deben a la presencia de retardos en el envío y recepción de las señales y a la difcultad de coordinación entre las tomas de carga de las unidades y la fijada por el CDEC.

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